As technology advances, new products and services are created that have new communication requirements in terms of throughput, signal quality and transmission delay. Many of these new use cases such as augmented reality/virtual reality (AR/VR), gaming, self-driving cars, remote medical imaging, etc., require low latency and reliability. For example, some transmissions require about a 1 millisecond end-to-end latency and/or lossless transmissions such that retransmissions occur if packets are lost. Most of these use cases utilize Transmission Control Protocol (TCP), where the end-to-end transport control keeps track of which packets are acknowledged and which packets require retransmission. If an acknowledgement signal (ACK) is not received within a timeout period for a packet, then the packet is retransmitted.
A new user plane for a future generation network (e.g., 5G) has end-to-end latency that is significantly less than HO duration and a small retransmission timeout period. As a result, traffic sources are more likely to retransmit packets already buffered in the network due to the mobility management mechanism, thereby causing excessive duplication in high data rate communications and more latency.
Problems that occur when HO duration (Th) is significantly greater than round trip time (RTT), that is, the duration for a small Internet Protocol (IP) packet to travel from a traffic source through the network to a destination, and back, will now be illustrated with reference to FIG. 1. FIG. 1 depicts a mobile communication network 16 wherein a UE 22 undergoes a HO from a first base station (e.g., a source E-UTRAN NodeB (SeNB)) 14a to a second base station (e.g., target eNB (TeNB)) 14b. In high-speed networks, a traffic source 20 sends a relatively large number of packets. The traffic source sets a retransmission timeout period as α×RTT (where α>1, but small). The traffic source is self-clocked by ACKs from the UE 22. In other words, the traffic source 20 sends more packets as more ACKs are received from the UE 22. Once a packet's retransmission timeout period expires, the subsequent in-flight packets also expire and are retransmitted and clocked by the ACK of earlier packets. During HO, in-flight packets are buffered in the network 16 and the UE 22 is in an outage state (e.g., the UE 22 cannot transmit or receive any packets). Since HO time is much greater than end-to-end retransmission timeout, all in-flight packets before the handover (i.e., P1 to PK) expire and are retransmitted by the traffic source 20, which creates congestion and more latency after HO is completed.